Emails that have not been authenticated by TLS encryption (transport layer security) will show this red unlocked icon, but that doesn’t necessarily mean that the sender is an evil spammer sneaking into your inbox.

What TLS encryption does is protect the security of email messages as they travel from sender to recipient. That encryption makes sure that the sender’s email remains private, preventing third parties from taking a peek at the message or tampering with it as it makes its way to its final destination.

So if you see this icon, and the message has anything to do with sensitive information (finances, passwords, etc.), you should be concerned and take steps to contact the sender about the insecure email. But outside of emails containing sensitive information, that scary lock icon may just be an indication that the email could be compromised or that sender isn’t taking its security as seriously as they should be.

Again, if you see the red unlocked icon, don’t immediately reach for the Send to Spam button, just take special note of that particular message. No need to panic, just keep your guard up.